1. Field of the Invention
The present invention relates to a manufacturing method for a light-propagating probe using a near-field microscope for measuring optical characteristics in a microscopic region of a material to be measured, as one type of probe microscope.
2. Description of the Related Art
Scanning probe microscopes, exemplified by Atomic Force Microscopes (AFM) and Scanning Tunnel Microscopes (STM) are widely adopted because they are capable of observing microscopic shapes on sample surfaces. However, conventional AFMs and STMs are suitable for high resolution shape observation of a sample surface, but can not measure the physical or chemical properties of a sample. Near field light is now being used as means for observing these type of sample properties.
For example, there have been efforts to measure optical characteristics and shape of a sample by bringing a probe made of an optical medium having a sharpened tip to within less than the light wavelength of the measurement sample, and a number of near-field microscopes have been proposed. As one of these devices, there has been proposed a device for observing surface shape by irradiating laser light from a sample surface so as to irradiate the entire rear surface of the sample, detecting evanescent light leaking to the sample surface by bringing a tip of a light fiber probe having a jogging mechanism, and measuring variations in strength of the evanescent light by scanning the probe so as to detect constant evanescent light or scanning the probe horizontally.
There has also been proposed a device for causing a tip of an optical fiber probe held vertically with respect to the sample to vibrate horizontally with respect to the sample surface, detecting variations in amplitude of vibrations caused by friction between the sample surface and the probe tip as displacement of the optical axis of laser light that is irradiated from the optical fiber tip and passes through the sample, and holding a distance between a probe tip and the sample surface constant by moving the sample using a jogging mechanism, to detect surface shape from the strength of signals input to a jogging mechanism, and measure optical permeability of a sample.
An optical fiber probe used in these near-field microscopes is a straight type, and various aspects and manufacturing methods for a straight optical probe are disclosed (for example, refer to patent document 1). One example is shown in FIG. 18. A tip section of an optical fiber comprised of a core 201 and clad 202 stretches from the outer periphery of the clad 202 to the center of the core 201, and is sharpened to a cone shape. There is a shaded cover layer 204 on the surface of an acute section 203, and an opening section (aperture) 205 at the tip of the acute section 203.
On the other hand, there has also been proposed a scanning near-field atomic force microscope for irradiating laser light from a tip of an optical fiber probe to a sample to detect the surface shape and measure optical characteristics of the sample, at the same time as functioning as an AFM, using a hook-shaped optical fiber probe as an AFM cantilever (for example, refer to patent document 2).
Patent document 1
International patent laid-open No. WO95/33207 (page 16-17, FIG. 4).
Patent document 2
Japanese patent laid-open No. Hei. 7-164542 (FIG. 18).
Among near-field microscopes using the straight optical fiber probe shown in FIG. 18, in the case of devices that perform distance control between a probe tip and the sample surface using evanescent light, since light intensity is used as sample height direction information there is the drawback that it is not possible to separate light intensity variations in the height direction of the sample and light intensity variations due to light absorption of the sample, and it is difficult to use such near-field microscopes as means for measuring physical and chemical properties of a sample. Also, in the case where there is severe unevenness on the sample surface, light may sometimes not be totally reflected at the sample surface, and this passing light causes interference at the sample surface and may hinder measurement.
In the case where the probe is made to vibrate horizontally, since the probe tip vibrates sideways, and particularly in cases such as when there is severe unevenness of the sample surface, there are limitations to improvement of resolution in the sideways direction.
On the other hand, it can be considered that in the case of a scanning near-field microscope using a hook-shaped optical fiber probe as an AFM cantilever, it is possible to observe measurements of surface shape and optical characteristics of a sample at high resolution, regardless of the presence or absence of light permeability or conductivity of the sample.
Here, since the straight optical fiber probe shown in FIG. 18 is straight, it is possible to form the acute section 203 comparatively easily. Also, formation of the shaded cover 204 and the opening section 205 is possible using one-time deposition using a rotating deposition jig. On the other hand, a hook-shaped optical fiber probe used in a scanning near-field atomic force microscope requires, in addition to advanced shaping technology for the hook shape, a lot of processes compared to a straight probe, such as forming the shaded cover for the hook-shaped formation, forming an opening, forming a reflecting surface to cause AFM operation, etc. Therefore, the manufacturing process becomes complicated, it is difficult to maintain reproducibility, and it is difficult to lower manufacturing cost.